What is an ecosystem?

In Content and Language Integrated Learning (CLIL) contexts, students are expected to express disciplinary knowledge in a second/foreign language. One construct that has proven useful for the identification and realization of language functions in disciplinary knowledge is Dalton-Puffer’s (2013) model of cognitive discourse functions (CDFs). Additionally, Systemic Functional Linguistics (SFL) has already been proven useful for distinguishing lexico-grammatical features that characterise different CDFs in CLIL students’ productions (e.g., Nashaat-Sobhy & Llinares, 2020; Evnitskaya & Dalton-Puffer, 2020). In this article, we use SFL to analyse the oral and written realisations of the CDF Define by 6th grade students participating in a CLIL program in Madrid, Spain. A total of 83 students responded to the same prompt (on science) in writing (in the form of a blog) as well as orally (in the form of an interview). In the oral interviews the co-construction of definitions by the students with the interviewer (researcher) and another peer are explored using the notion of Legitimation Code Theory and the concept of semantic waves (Maton, 2013). The analysis of students’ definitions is also related to primary CLIL teachers’ evaluations using comparative judgement.